Form tool grinding fixture



A ril 13, 1937. H. PELPHREY FORM TOOL GRINDING FIXTURE Filed May '7,1930 4 Sheets-Sheet 1 INVENTOR Harry Fe Zrhrc y.

A] ab "Az TT0RNEY5- 4 Sheets-Sheet 2 H. PELPHREY FORM TOOL GRINDINGFIXTURE Filed May '7, 1950 INVENTOR flarr y Pep/rrcy.

@240 TORNEY5.

April 13, 1937.

April 13, 1937. H. PELPHREY FORM TOOL GRINDING FIXTURE Filed May 7, 19304 Sheets-Sheet 3 INVENTOR Hal y elpiirfy.

W/vw A TORNEYS April 13, 1937. H. PELF'HREY 2,075,742

FORM TOOL GRINDING FIXTURE Filed May 7, 1930 4 Sheets-Sheet 4 56INVENTOR fla r y Palpirrqy,

ATTORNEYS.

Patented Apr. 13, 1937 UNITED STATES PATENT OFFICE Harry mesne assignmenPelphrey, Detroit, Micln,

ts, to Michigan pany, a corporation of Delaware assignor, by

Tool Com- Application May I, 1930, SerialNo. 450,501

2Claims.

This invention relates to an improved fixture for guiding a grindingwheel shaping member.

The main objects of the invention are to provide an improved fixture ofthis kind for positioning a cutting member so as to form a predeterminedcurvature on the periphery of an abrasive wheel for grinding a formingtool thereby which is adapted to cut on a hob; to provide improved meansfor shaping grinding wheel so as to form a tool of this kind by whichthe teeth of a hob are conditioned to produce splines having radiallyoflset sides on a shaft; to provide apparatus of this type in which aslight adjustment may be conveniently made for predetermining the widthof the ultimate splines; and to provide improved means for compensatingin the shaping of the contour of the grinding wheel for the clearanceangle of the forming tool necessary to obtain proper cutting operationtherewith.

An illustrative embodiment of my invention is shown in the accompanyingdrawings, in which Fig. 1 is a front elevation of a fixture embodying myinvention.

Fig. 2 is a side elevation of the fixture shown in Fig. l.

Fig. 8 is a plan view of the fixture.

Fig. 4 is a side elevation, partly in section, showing my improvedfixture in an operative 30 position.

Fig. 5 is a side elevation of a diamond cutting element holder.

Fig. 6 is a rear elevation of the holder in Fig. 5.

Fig. 7 is a fragmentary perspective view of a hob.

Fig. 8 is a perspective view of a hob forming tool.

Fig. 9 is a diagrammatic view, partly in sec- 40 tion, illustrating theoperation in which the teeth of the hob are cut by the forming tool.

Fig. 10 is a diagrammatic perspective view illustrating the operation inwhich the periphery of a grinding wheel is shaped to grind the hob 45teeth forming tool.

Fig. 11 is a diagrammatic front end view of the apparatus shown inperspective in Fig. 10, illustrating the locus of the cutting edge ofthe grinding wheel shaping element.

Fig. 12 is a perspective view of a splined end of a shaft.

The engagement between a hob and a spline shaft being cut thereby may beconsidered to include the same relative movements as exist be- 55 tweenan interengaged worm and a worm wheel,

shown and shape the teeth the worm wheel in such a case having straightand radially oflset tooth side faces. If a true rolling action is toexist between the worm and wheel in such a case, the sides of the wormteeth must be formed to correspond in curvature to a cycloidal curve ofpredetermined generating radius.

Employing this as a basis it follows that if we form the side faces 01'a hob to the shape or a predetermined part of a cycloidal curve ofproper generating radius, the hob will, in cutting a properlycooperating shaft, form thereon splines having straight and radiallyofiset side faces.

Employing this as a basis the problem encountered is to shape a the hobteeth which forming tool will be provided with a cutting edgecomplementary in shape to the desired shape of the hob teeth. Thispresents a problem which I find may best be solved by grinding the toolto shape and accordingly, the present invention is primarly directed toa fixture for providing a grinding wheel with a contour complementary tothe contour of the cutting edge of the forming tool (and thereforeidentical to the contour of the sides of the hob teeth) certainpractical requirements being taken into consideration incarrying outthese variofis steps such as, for instance, the inclination of theforming tool relative to the surface upon which it is working.

The fixture includes a support I having a base 2 on which a seat 3 isformed at an inclination with respect to the sides of the support andbase. Formed on the upper side of the support I is a dovetail projection4 which extends into a. similarly shaped recess 5 in the lower side of acarriage 6 which is slidably mounted on the support I. The recess 5 ofthe carriage is somewhat wider than the dovetail projection 4 01' thesupport thereby providing a space between the adjacent rear sides of therecess 5 and projection 4 in which a gib I is located and secured aainst displacement by a bolt 8 having a lock nut 8 thereon. Mounted onthe front side of the carriage 6 is a dust plate Ill which extendslongitudinally of the carriage and support i and overlaps the upper edgeportion of the front side of the support.

A tool holder or guide having a shaft H journaled in a laterallyextending passage l2 formed in the carriage 6 is supported by thecarriage and adapted to be shifted linearly therewith relative to thesupport I and base 2. Provided on the rear end portion of the shaft IIis a pair of drums I3 and I I on which the adjacent ends of forming toolfor shaping a pair of flexible metal straps or bands I5 and I6respectively are secured, the strap l5 being wrapped in a clockwisedirection on the drum 3 and the strap I6 being wrapped in acounterclockwise direction on the drum II. The outer end of the strap I5is secured by a screw IS in a clamping member I! which is adjustablymounted by a bolt M3 on a bracket or support I9 at the left side of thefixture as viewed in Fig. l and the strap I6 is rigidly secured to alug20 on a bracket 2| mounted at the right end of the fixture. The strapsl5 and I5 may be suitably tensioned by adjustment of the member l1 andnut l8. Rigidly mounted on the front end of the shaft II is a guideplate 22 having a guide bar 23 thereon which is adjustably held in adesired position by a bolt 24 extending through a slot 25 in the bar andthreaded in an aperture in the plate 22.

In operation, the inclined lower side of the base 2 of the fixture isseated on the bed 26 of a machine which has a spindle 21, with thecarriage 6 arranged to slide longitudinally of the bed substantiallyparallel to the spindle 21. A grinding wheel 28 is then rigidly mountedon the spindle 21 by which it is rotated about its normal axis ofrotation as illustrated in Fig. 10.

A cutting tool comprising a shank part 29 having an aperture 30 in oneside thereof in which is seated a cutting element 3| preferably having adiamond cutting point 32, is mounted for reciprocating movement on theguide plate 22 adjacent the edge of the guide bar 24. Formed in the endof the shank 29 is an aperture which communicates with the aperture 3|)and in it is threaded a set screw 33 for firmly holding the cuttingelement 3! in axially adjusted position.

During rotation of the wheel 23, the guide plate 22 and shaft II aremanually rotated about the axis of the shaft so as to change theposition of the path of the cutting element 3! with respect to the wheel28 and the cutting tool is held by hand against the guide plate 22 andguide bar 23 and manually reciprocated. This action subjects differentportions of the wheel to the cutting action of the diamond point 32which moves on various tangents to a cycloidal curve. When the guideplate is rotated in a counter-clockwise direction as viewed in Fig. 10,the inner end of the strap or band 16 is wound upon the drum l4 and thecorresponding end of the band I5 is unwrapped from the drum 13. Thisaction causes the carriage together with the guide plate supportedthereon to be moved linearly to the right as viewed in Fig. 1.

The combined and related lineal and rotary movements of the shaft If andguide plate 22 cause the cutting point 32 of the element 3| to travelduring its reciprocation in paths which are tangent to a cycloidal curve34 such as would be developed by rolling a generating circle 35 on astraight line, the generating circle illustrated in Fig. 1]corresponding in diameter to the drums i3 and M on the shaft H. Theshaft II and guide plate 22 are manually rotated into desired positionand the cutting tool is reciprocated while in engagement with the guidebar 23, thereby moving the cutting point 32 along a plurality of pathswhich are tangent to the cycloidal curve 34 the guide plate is placed invarious positions and the diamond point 32 dresses the side peripheralportion of the wheel 28 to a. curvature which corresponds with thecurvature of the cycloldal curve 3'3.

In this manner one side of the wheel 23 adjacent the perlphery thereofis dressed so as to grind a curvature on the forming tool 36 shown inFig. 8 which is complementary to the cycloidal curvature required andthe side faces of the teeth 31 of the hob 38 illustrated in Fig. 7.Separate tools may be provided for forming the respectively oppositesides of the teeth 31, each tool being formed in the above manner orboth faces of a tool of the form shown in Fig. 8 may be groundseparately on the side cutting face of the wheel by first grinding oneface; and then turning the tool through 180 about its longitudinal axisand applying the other face thereof to the wheel at an oppositeinclination to the first grinding position.

In using the tool 36 to shape the side faces of the hob teeth, the toolis mounted on a conventional machine which is adapted to move it axiallyof its length as illustrated by the arrow 39 in Fig. 9, relative to 2.bob blank 40 during timed rotation of the latter. The extremity of theforming tool 36 may have a cutting edge 4| for dressing the metalbetween the bases of laterally adjacent teeth of the blank on thearcuate line 62 and may have a similar cutting edge 43 provided at theinner end of the cycloidal cutting edge 46 for correspondingly dressingthe outer periphery of the teeth. The tool 36 is moved inwardly towardsthe center of the hob blank further at the rear end of each tooth thanat the front end portion or cutting edge thereof so as to provide theusual clearance.

During the shaping of the teeth of the hob it is necessary to have thefaces of the cutting tool 36 adjacent the cutting edges thereof at aninclination approximately 25 degrees to the surfaces upon which thecutting edges work, as indicated at 45 in Fig. 9. This angle is usuallyknown as the clearance angle. In order to compensate, in the forming ofthe cutting surface of the grinding wheel, for the angular path ofmovement of the grinding wheel relative to a plane normal to the lengthof the forming tool in order to'produce this clearance angle, the shaftH is positioned, by virtue of the inclined seat 3 of the base 2, at aninclination to the plane which includes the axis of the spindle 21 andthe radius 21' of the wheel 23 with which the cutting point 32 registersas shown in Fig. 4, equal to the clearance angle.

The width of the spline that a hob cut by a forming tool ground in theabove manner will produce may be predetermined by adjustably positioningthe grinding point 32 of the cutting element 3| with respect to theshank 29 in which the latter is mounted. The distance between the point32 and the dotted line 46 which extends through the axis of the shank Hand is parallel of the guiding edge of the guide bar 23 is equal toone-half the width of the resulting spline.

With the above apparatus it is possible to move the cutting point of atool along various paths which are tangent to an accurately developedcycloidal curve so that the curve forms the boundary on which thecutting surface of the grinding wheel is dressed. A hob tooth formed bya forming tool which has been ground on a wheel having a cutting surfaceof cycloidal curvature is capable of forming splines on a shaft havingradial offset sides.

Formal changes may be made in the specific embodiment of the inventiondescribed without departing from the spirit or substance of the ing hobforming member, a support, a rotatable tool guide shiftably mounted onsaid support, comprising a shaft, drums on said shaft. :1 pair offlexible bands each wound on one of said drums 10 in an oppositedirection relative to the other band and secured to said support forshifting said tool guide linearly during rotation thereof, and areciprocating cutting tool on said guide. the cutting edge of said toolbeing retained by the re- 15 lated lineal and rotary movement of saidguide in various paths which are tangent to a cycloidal curve.

2. A fixture including a support. a carriage shiitably mounted on saidsupport, a tool holder journaled in said carriage having an exposed periheral portion concentric with its axis of rotation and having a toolguiding member spaced from said axis, a cutting tool supported on saidguiding member, and a band fixed at one end to said support and at itsother end to said exposed peripheral portion !or shitting said carriageand tool holder linearly in one direction transversely of the axis ofrotation of the latter an amount equal to the circumferential travel ofa point on said tool holder in an opposite direction during rotationthereof.

HARRY PELPHREY.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,742.

April 13. 1937.

HARRY PELPHREY.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Page 2.,

first column, line 6, strike out the reference numeral 16"; and that thesaid Letters Patent srould be read with this correction therein that thesame may conform \to the record of the case in the Patent Office. j

Signed and sealed this 1st day of June, A. D. 1937.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.

ing hob forming member, a support, a rotatable tool guide shiftablymounted on said support, comprising a shaft, drums on said shaft. :1pair of flexible bands each wound on one of said drums 10 in an oppositedirection relative to the other band and secured to said support forshifting said tool guide linearly during rotation thereof, and areciprocating cutting tool on said guide. the cutting edge of said toolbeing retained by the re- 15 lated lineal and rotary movement of saidguide in various paths which are tangent to a cycloidal curve.

2. A fixture including a support. a carriage shiitably mounted on saidsupport, a tool holder journaled in said carriage having an exposed periheral portion concentric with its axis of rotation and having a toolguiding member spaced from said axis, a cutting tool supported on saidguiding member, and a band fixed at one end to said support and at itsother end to said exposed peripheral portion !or shitting said carriageand tool holder linearly in one direction transversely of the axis ofrotation of the latter an amount equal to the circumferential travel ofa point on said tool holder in an opposite direction during rotationthereof.

HARRY PELPHREY.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,742.

April 13. 1937.

HARRY PELPHREY.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Page 2.,

first column, line 6, strike out the reference numeral 16"; and that thesaid Letters Patent srould be read with this correction therein that thesame may conform \to the record of the case in the Patent Office. j

Signed and sealed this 1st day of June, A. D. 1937.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.

